1. Technical Field
The present disclosure relates to a system and method for dynamically accounting for the effect of flow profile of fluid, such as gas or liquid, on the calibration of ultrasonic flowmeters in the region between any defined pipe configuration, and the downstream location at which the flow profile becomes fully developed. Based on this system and method, an accurate calibration factor can be determined so as to assure accurate flow measurement.
2. Discussion of Related Art
Clamp-on ultrasonic flowmeters, which are installed on pipes to measure fluid low, have been installed without pre-calibration, without flow conditioning and in locations of convenience or where no choice of location may be made. Known methods of mounting and clamping ultrasonic flowmeters to pipes are described, for example, in U.S. Pat. No. 4,425,803 to Baumoel, entitled “Transducer Structure And Mounting Arrangement For Transducer Structure For Clamp-On Ultrasonic Flowmeters”; U.S. Pat. No. 6,273,373 to Baumoel, entitled “Device for Clamping A Transducer to a Pipe,” and U.S. Pat. No. 6,418,796 to Baumoel, entitled “Sonic Flow Measurement Apparatus For Tubes Including Sonically Matched Plates,” which are commonly owned and incorporated herein by reference.
As fluid flow proceeds down a pipe, the effect of friction, or drag, of the pipe wall on the layers of fluid in contact with the wall, slows down the flow adjacent to the pipe wall relative to a higher flow rate at the center of the pipe. Thus, if allowed to flow for a given length, the shape of the flow profile will reach a condition where the relative flow across the diameter of the pipe will reach a fully developed shape that remains the same as flow proceeds further down the pipe. This shape is a function of the Reynolds number, which is based on velocity, viscosity and density of the fluid and characteristic dimension (e.g., pipe diameter). The fully developed shape is generally “pointier” for lower Reynolds numbers (e.g., a convex flow profile) and flatter for higher Reynolds numbers (e.g., a flat flow profile).
As a result of the difference in flow rates between the area near the pipe wall and the central portion of the pipe results, an improperly calibrated flowmeter outputs inaccurate flow measurements.
Under these circumstances, there is need to accommodate the effect of the local flow profile on meter calibration.